Credits:
This vulnerability was discovered and researched by Esteban Martinez Fayo of
Application Security Inc.

Details:

There is a flaw in the way that Authentication Session Keys are generated and
protected by Oracle Database Server during the authentication process. It is
possible to use this flaw to perform unlimited password guesses (cracking) of
any user password in a similar way as if the password hash would be available.
All users that are authenticated by the database using logon protocol version
11 are affected by this vulnerability. This includes all users created with
the "IDENTIFIED BY" clause, including the SYS user.
The attack can be performed remotely without the need of a valid username and
password. The attacker just needs to know the SID of the database and the
name of a valid user. The attack can be done with just a few network packets
and without leaving any trace in native auditing facilities.

Workaround:
Some possible workarounds:
1) Use strong user passwords. A strong password will make password guessing
more difficult (or impossible) to solve in reasonable time.
2) Use external authentication. Only users that are authenticated by the
database are affected by this vulnerability. Users that are authentication by
external means are not affected; this includes users authenticated by the
Operating System and the Network (SSL or third-parties like Kerberos).
3) Disable protocol version 11 and use version 10 or lower instead. To do
this, set initialization parameter SEC_CASE_SENSITIVE_LOGON to FALSE.
See https://www.teamshatter.com/?p=3951 for more information about the
workarounds.

AppSecInc is a pioneer and leading provider of database security
solutions for the enterprise.
By providing strategic and scalable software-only solutions -
AppDetectivePro for auditors and IT advisors, and DbProtect for the
enterprise - AppSecInc supports the database security lifecycle for some
of the most complex and demanding environments in the world across more
than 1,300 active commercial and government customers.

Leveraging the world's most comprehensive database security
knowledgebase from the company's renowned team of threat researchers,
TeamSHATTER, AppSecInc products help customers achieve unprecedented
levels of data security from nefarious or accidental activities, while
reducing overall risk and helping to ensure continuous regulatory and
industry compliance.

Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
author nor the publisher accepts any liability for any direct, indirect,
or consequential loss or damage arising from use of, or reliance on,
this information.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.11 (MingW32)